If you want to know what is kernel version of system
$ uname -r
If you want to know what was gcc version with which this kernel is built and who was that person
$ cat /proc/version
Linux version 3.8.0-34-generic (buildd@lamiak) (gcc version 4.7.3 (Ubuntu/Linaro 4.7.3-1ubuntu1) ) #49-Ubuntu SMP Tue Nov 12 18:02:44 UTC 2013
buildd@lamiak is ID of person who has build 3.8.0-34-generic kernel on Tue Nov 12 18:02:44 UTC 2013 with gcc version 4.7.3. It also indicates that this is Ubuntu distribution.
If you want to know about distribution of your system
$ cat /etc/os-release
VERSION="13.04, Raring Ringtail"